Dissolved and particulate metals (Fe, Zn, Cu, Cd, Pb) in two habitats from an active hydrothermal field on the EPR at 13 degrees N

The distribution of Fe, Cu, Zn, Pb, Cd between the dissolved (<2 microm) and the particulate (>2 microm) fractions was measured after in-situ filtration in two hydrothermal habitats. The total metal concentration ranges exhibit a clear enrichment compared with the seawater concentration, accounting for the hydrothermal input for all the metals considered. Iron is the predominant metal (5-50 microM) followed by Zn and Cu. Cd and Pb are present at the nM level. At the scale studied, the behavior of temperature, pH and dissolved iron is semi-conservative whereas the other dissolved and particulate metals are characterized by non-conservative patterns. The metal enrichment of the >2 microm fraction results from the settlement and accumulation of particulate matter close to the organisms, acting as a secondary metal source. The enrichment observed in the dissolved fraction can be related to the dissolution or oxidation of particles (mainly polymetallic sulfide) or to the presence of small particles and large colloids not retained on the 2 microm frit. SEM observations indicate that the bulk particulate observed is characteristic of crystalline particles settling rapidly from the high temperature smoker (sphalerite, wurtzite and pyrite), amorphous structures and eroded particles formed in the external zone of the chimney. Precipitation of Zn, Cu, Cd and Pb with Fe as wurtzite, sphalerite and pyrite is the main process taking place within the area studied and is semi-quantitative. The distribution of the dominant observed fauna has been related to the gradient resulting from the dilution process, with the alvinellids worms colonizing the hotter and more variable part of the mixing zone, but also to the metallic load of the mixing zone. Dissolved and particulate metal concentrations are therefore necessary abiotic factors to be studied in a multiparametric approach to understand the faunal distribution in hydrothermal ecosystems.     

Paclitaxel-loaded microparticles for intratumoral administration via the TMT technique: preparation, characterization, and preliminary antitumoral evaluation

In our pursuit to develop suitable therapeutic particulate systems for intratumoral delivery by the targeted multi-therapy (TMT) technique, we describe the preparation of paclitaxel-loaded poly(D,L-lactic-co-glycolic) acid (PLGA) microparticles (MPs) (drug loading 35-38%, wt/wt; size 0.7-5 microm). Magnetite (15%, wt/wt) was also incorporated in some preparations for a future magnetic resonance imaging (MRI)-guided delivery. X-ray diffraction (XRD) and differential scanning calorimetry (DSC) experiments showed that paclitaxel was not encapsulated in its initial crystalline form. The paclitaxel in vitro release pattern showed a biphasic tendency with a burst effect followed by a sustained release (28% released amount after 1 month), which was accompanied with MP erosion and degradation signs as confirmed by scanning electronic microscopy (SEM) micrographs. The paclitaxel-loaded MPs demonstrated a dose-dependent antitumor effect on human uterine cancer cells, with an IC(50) value relatively close to that of commercial Taxol. This paclitaxel delivery system represents a potent antiprofilerative and radiosensitizer agent for intratumoral administration via the TMT technique.     

新的超声立体视觉数据增强技术

针对超声成像噪声大、数据质量严重退化的特点,提出了一种新颖的非稳定度度量算法,该算法通过加强图像变化较大的部分来实现超声数据的增强.给出了输入信号信噪比不同情况下非稳定度算子与Deriche算子的输出仿真结果;通过兔子肝脏和12周胎儿的实际数据计算,得到了二者经非稳定度算子处理前后的超声立体视觉图像.研究结果表明,非稳定度数据增强技术对噪声不敏感,通过对比处理前后的图像可清晰地看出非稳定度算子能够有效地改善超声立体视觉成像的质量.     

Physicochemical characteristics and biological activities of seasonal atmospheric particulate matter sampling in two locations of Paris

Fine particulate matter present in urban areas seems to be incriminated in respiratory disorders. The aim of this study was to relate physicochemical characteristics of PM2.5 (particulate matter collected with a 50% efficiency for particles with an aerodynamic diameter of 2.5 microm) to their biological activities toward a bronchial epithelial cell line 16-HBE. Two seasonal sampling campaigns of particles were realized, respectively, in a kerbside and an urban background station in Paris. Sampled-PM2.5 mainly consist of particles with a size below 1 microm and are mainly composed of soot as assessed by analytical scanning electron microscopy. The different PM2.5 samples contrasted in their PAH content, which was the highest in the kerbside station in winter, as well as in their metal content. Kerbside station samples were characterized by the highest Fe and Cu content, which appears correlated to their hydroxyl radical generating properties measured by electron paramagnetic resonance. Particles were compared by their capacity to induce cytotoxicity, intracellular ROS production, and proinflammatory cytokine release (GM-CSF and TNF-alpha). At a concentration of 10 microg/cm2, all samples induced peroxide production and cytokine release to the similar extent in the absence of cytotoxicity. In conclusion, whereas the PM2.5 samples differ by their PAH and metal composition, they induce the same biological responses likely either due to components bioavailability and/ or interactions between PM components.     

Short- and long-term dynamics of the toxic potential and genotypic structure in benthic populations of Microcystis

Microcystis colonies are known to overwinter on the surface of the sediment of freshwater ecosystems. However, little is known about the genotypic and toxicological dynamics of Microcystis populations during this benthic life stage. In this study, we report a two-year-long survey of benthic populations of Microcystis, which had spent from a few days to more than six years in the sediment. In order to avoid any interaction with the planktonic proliferations, we chose two deeply buried benthic populations, which could be easily dated. Quantitative PCR on mcyB gene and protein phosphatase inhibition assays were performed to measure their toxic potential, and their genotypic structure was assessed by Capillary Electrophoresis-Single Strand Conformation Polymorphism (CE-SSCP), based on 16S-23S Intergenic Transcribed Spacer (ITS). The microcystin content of the cells seemed to change sharply during the first few months of benthic survival, whereas this content was low and decreased steadily after several years of benthic life. No genetic selection was observed in either the proportion of potentially toxic clones or the ITS sequences for any of the populations considered. From these results, the benthic life stage of Microcystis appears to preserve the structure and the composition of the population over a far larger time scale than classical overwintering period. Finally, some genotypes were common in both of the benthic populations, even though they originated from planktonic blooms that had developed five years apart, suggesting a major overlap of planktonic proliferations in successive years.     

Do sewage treatment plant discharges substantially impair fish reproduction in polluted rivers?

Sewage treatment plants are frequently associated with the release of xenobiotics and, consequently, with alterations of the reproductive function induced by many of these substances in aquatic organisms. In order to assess the impacts of sewage treatment plant (STP) discharges in polluted rivers, two sentinel species (gudgeon Gobio gobio and stoneloach Barbatula barbatula) were caught during their reproductive cycle upstream and downstream two STPs (STP1--Goffontaine, STP2--Wegnez). Gonadosomatic index, histological (testicular and ovarian stages, atretic follicles, intersexuality) and endocrine (sex steroids, aromatase activity, alkali-labile phosphorus) parameters were assayed. In brief, the results revealed no systematic significant differences (p<0.05) between upstream and downstream sites, whatever the STP, species or sampling period. However, stoneloach females displayed some signs of reproductive impairment and endocrine disruption downstream STP1 (reduced GSI, oocyte diameter and ALP concentrations, increased proportion of atretic follicles) and STP2 (changes in gonadal aromatase activity and plasma levels of 11-KT and T). Few significant changes were observed for gudgeon males and females while there were no significant differences between upstream and downstream sites for stoneloach males. Moreover, plasma E(2) concentrations recorded in gudgeon males sampled in all sites were as high as in females and this was confirmed by high ALP levels. Besides, spermatogenesis of gudgeon males was delayed in STP1 upstream and downstream sites compared to the corresponding sites in STP2. These observations for gudgeon males do not seem related to STP discharge but to a probable estrogenicity of the river. Therefore, as shown by the results, stoneloach seemed more sensitive than gudgeon to STP discharges. In the present study, sewage treatment plant discharges do not substantially impair fish reproduction. In this respect, caution is required when generalising negative impacts of STP discharges.     

Simulators for medical training: application to vascular ultrasound imaging

Whilst computers are more and more used in the medical and surgical domains, medical education is still very conservative. However, new information technology could bring a lot to this area. In particular, simulators are of paramount interest: they would allow one both to experiment with surgical or imaging techniques for a wide range of pathologies without the need for patients and to quantitatively evaluate the trainees' performances. Ultrasound imaging is a typical area where virtual reality may change educational uses. This paper describes an ultrasound imaging simulator dedicated to the training of physicians for the detection of deep venous thromboses of the lower limbs. Like this one, a lot of other pathologies of soft tissue are diagnosed using ultrasound imaging. Because this examination is difficult and operator‐dependent, developing a simulator is very useful to give common databases of pathological samples on which physicians can both experiment with image acquisition and evaluate their understanding of clinical cases. Real‐time simulation is mandatory. An ultrasound imaging simulator has been developed and is being tested. This paper presents the hardware and software components of the simulator and describes the status of this project. Copyright © 2000 John Wiley & Sons, Ltd.